Objective   Bioinformatics and expressions of the nitrate reductase gene of kenaf(Hibiscus cannabinus) were studied for breeding varieties highly efficient in nitrogen utilization.

  Method  From the leaf of kenaf 349, the coding sequences (CDS) of HcNiR was amplified by PCR. Bioinformatics method was applied to analyze the amino acid sequences, protein transmembrane structure, protein signal peptide, high-level structures, and homologous evolutionary tree associated with the gene, while the expression in various tissues detected by qRT-PCR.

  Result  The full length of HcNiR cDNA was 1395 bp encoded 464 amino acids. The amino acid sequence contained two conserved nitrite and sulfite reductase 4Fe-4S domains and two conserved nitrite/sulfite reductase ferredoxin-like half domains. The predicted stable, hydrophilic HcNiR protein with an isoelectric point of 5.49 and molecular weight of 51.68 kDa had no transmembrane domain or signal peptide. It contained 26 potential phosphorylation sites in a secondary structure that consisted of more than 70% in the forms of alpha helix and irregular coils. The amino acid sequence of HcNiR was 97.37% homologous with that of H. syriacus, and both included nitrite and sulfite reductases iron-sulfur/siroheme-binding sites. The phylogenetic tree on HcNiR showed it closely related to HsNiR. The HcNiR expression was higher in the leaves than in the roots of a kenaf plant.

  Conclusion   HcNiR contained two conserved nitrite and sulfite reductase 4Fe-4S domains and two conserved nitrite/sulfite reductase ferredoxin-like half domains. The gene was abundantly expressed in the kenaf leaves and speculated to be mainly involved in the process of primary nitrogen assimilation.